Transfer of High-Temperature-Sputtered BiFeO Thin Films onto Flexible Substrates Using α-MoO Layers.

Inducing external strains on highly oriented thin films transferred onto mechanically deformable substrates enables a drastic enhancement of their ferroelectric, magnetic, and electronic performances, which cannot be achieved in films on rigid single crystals. Herein, the growth and diffusion behaviors of BiFeO thin films grown at various temperatures is reported on α-MoO layers of different thicknesses using sputtering. When the BiFeO thin films are deposited at a high temperature, significant diffusion of Fe into α-MoO occurs, producing the FeMoO phase and suppressing the maintenance of the 2D structure of the α-MoO layers. Although lowering the deposition temperature alleviates the diffusion yielding the survival of the α-MoO layer, enabling exfoliation, the BiFeO is amorphous and the formation of the FeMoO phase cannot be suppressed at the crystallization temperature. High-temperature-grown BiFeO thin films are successfully transferred onto flexible substrates via mechanical exfoliation by introducing a blocking layer of Au and measured the ferroelectric properties of the transferred films.